PRELIMINARY
CYW43340
2.4 Power-Off Shutdown
The CYW43340 provides a low-power shutdown feature that allows the device to be turned off while the host, and any other devices
in the system, remain operational. When the CYW43340 is not needed in the system, VDDIO_RF and VDDC are shut down while
VDDIO remains powered. This allows the CYW43340 to be effectively off while keeping the I/O pins powered so that they do not draw
extra current from any other devices connected to the I/O.
During a low-power shut-down state, provided VDDIO remains applied to the CYW43340, all outputs are tristated, and most inputs
signals are disabled. Input voltages must remain within the limits defined for normal operation. This is done to prevent current paths
or create loading on any digital signals in the system, and enables the CYW43340 to be fully integrated in an embedded device and
take full advantage of the lowest power-savings modes.
Two signals on the CYW43340, the frequency reference input (WRF_XTAL_CAB_OP) and the LPO_IN input, are designed to be high-
impedance inputs that do not load down the driving signal even if the chip does not have VDDIO power applied to it.
When the CYW43340 is powered on from this state, it is the same as a normal power-up and the device does not retain any information
about its state from before it was powered down.
2.5 Power-Up/Power-Down/Reset Circuits
The CYW43340 has two signals (see Table 2) that enable or disable the Bluetooth and WLAN circuits and the internal
regulator blocks, allowing the host to control power consumption. For timing diagrams of these signals and the required
power-up sequences, see Section 19.: “Power-Up Sequence and Timing,” on page 87.
Table 2. Power-Up/Power-Down/Reset Control Signals
Signal
Description
WL_REG_ON
This signal is used by the PMU (with BT_REG_ON) to power up the WLAN section. It is also OR-gated with the
BT_REG_ON input to control the internal CYW43340 regulators. When this pin is high, the regulators are enabled
and the WLAN section is out of reset. When this pin is low, the WLAN section is in reset. If BT_REG_ON and
WL_REG_ON are both low, the regulators are disabled. This pin has an internal 200 k pull-down resistor that
is enabled by default. It can be disabled through programming.
BT_REG_ON
This signal is used by the PMU (with WL_REG_ON) to decide whether or not to power down the internal
CYW43340 regulators. If BT_REG_ON and WL_REG_ON are low, the regulators will be disabled. This pin has
an internal 200 k pull-down resistor that is enabled by default. It can be disabled through programming.
Document Number: 002-14943 Rev. *L
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